Quantitatively Monitoring of Seasonal Frozen Ground Freeze-thaw Cycle
Using Ambient Seismic Noise Data
Abstract
Seasonal frozen ground freeze-thaw cycles in cold regions are an
essential indicator of climate change, infrastructure, and ecosystems in
the near-surface critical zone (CZ). As a non-invasive geophysical
method, the ambient noise seismic method estimates the relative velocity
variations (dv/v) based on coda waves or ballistic waves, providing new
insights into the seasonal frozen ground changes in the soil properties
and hydrology data, such as soil moisture content (SMC), temperature,
and groundwater level. Due to the dv/v lack of accurate depth
information and average over tens of days at low frequencies, it is
challenging to provide the needed temporal-spatial resolution for the
micrometer-level frozen ground variation. In this work, we combine the
1D linear three-component seismic array and hydrological sensor to
conduct seasonal frozen ground freeze-thaw monitoring experiments.
Besides the conventional dv/v information, we calculate surface-wave
(SW) dispersion curve variations (dc/c), which are more sensitive to SMC
and can characterize the daily air temperature variations. Meanwhile,
the horizontal-to-vertical spectral ratio (HVSR) amplitude and seismic
attenuation also show highly consistent changes to the freeze-thaw
processes. This work demonstrates that the different ambient noise
seismic information (dc/c, HVSR, and attenuation) provide robust
observations for hydrogeological monitoring, such as air temperature,
SMC, and groundwater level changes during seasonal freeze-thaw
processes.